UPX - the Ultimate Packer for eXecutables.
INTRODUCTION ============ UPX is an advanced executable file compressor. UPX will typically reduce the file size of programs and DLLs by around 50%-70%, thus reducing disk space, network load times, download times and other distribution and storage costs. Programs and libraries compressed by UPX are completely self-contained and run exactly as before, with no runtime or memory penalty for most of the supported formats. UPX supports a number of different executable formats, including Windows 95/98/ME/NT/2000/XP/CE programs and DLLs, DOS programs, and Linux executables and kernels. UPX is free software distributed under the term of the GNU General Public License. Full source code is available. UPX may be distributed and used freely, even with commercial applications. See the UPX License Agreement for details. UPX is rated number one in the well known Archive Comparison Test. Visit http://compression.ca/ . UPX aims to be Commercial Quality Freeware. SHORT DOCUMENTATION =================== 'upx program.exe' will compress a program or DLL. For best compression results try 'upx --brute program.exe'. Please see the file UPX.DOC for the full documentation. The files NEWS and BUGS also contain various tidbits of information. DISCLAIMER ========== UPX comes with ABSOLUTELY NO WARRANTY; for details see the file LICENSE. Having said that, we think that UPX is quite stable now. Indeed we have compressed lots of files without any problems. Also, the current version has undergone several months of beta testing - actually it's almost 8 years since our first public beta. This is the first production quality release, and we plan that future releases will be backward compatible with this version. Please report all problems or suggestions to the authors. Thanks. THE FUTURE ========== - AArch64 (64-bit ARM) for Linux and iOS. - The Linux approach could probably get ported to a lot of other Unix variants, at least for other i386 architectures it shouldn't be too much work. If someone sends me a fresh hard disk and an official FreeBSD/OpenBSD/NetBSD/Solaris/BeOS... CD I might take a look at it ;-) - We will *NOT* add any sort of protection and/or encryption. This only gives people a false feeling of security because by definition all protectors/compressors can be broken. And don't trust any advertisement of authors of other executable compressors about this topic - just do a websearch on "unpackers"... - Fix all remaining bugs - keep your reports coming ;-) - See the file PROJECTS in the source code distribution if you want to contribute.
frm https://github.com/upx/upx
https://github.com/upx/upx/releases/latest
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UPX is a free, portable, extendable, high-performance executable packer for several executable formats.
Please also see the Wikipedia entry for some more background info.Blog Posts
- 23 Jan 2020 » UPX 3.96 released
- 26 Aug 2018 » UPX 3.95 released
- 12 May 2017 » UPX 3.94 released
- 29 Jan 2017 » UPX 3.93 released
- 11 Dec 2016 » UPX 3.92 released
- 01 Sep 2016 » Moving to GitHub
Overview
UPX achieves an excellent compression ratio and offers very fast decompression. Your executables suffer no memory overhead or other drawbacks for most of the formats supported, because of in-place decompression. UPX strengths in a nutshell:
- excellent compression ratio: typically compresses better than WinZip/zip/gzip, use UPX to decrease the size of your distribution!
- very fast decompression: ~10 MB/sec on an ancient Pentium 133, ~200 MB/sec on an Athlon XP 2000+.
- no memory overhead for your compressed executables because of in-place decompression.
- safe: you can list, test and unpack your executables. Also, a checksum of both the compressed and uncompressed file is maintained internally.
- universal: UPX can pack a number of executable formats.
- portable: UPX is written in portable endian-neutral C++.
- extendable: because of the class layout it's very easy to add new executable formats or new compression algorithms.
